The invention relates to a fluidic oscillator that is symmetrical about a longitudinal plane of symmetry P comprising an enclosure defining an oscillation chamber and having an inlet opening and an outlet opening through which the fluid flows, which openings are in alignment in said plane P in a xe2x80x9clongitudinalxe2x80x9d direction, said inlet opening being implemented in the form of a slot that is narrow in a direction transverse to said plane P, and elongate in a direction contained in said plane P and perpendicular to said longitudinal direction.
Fluidic oscillators are well known. Document EP 0 381 344 describes a fluidic oscillator operating on the basis of the Coanda effect. The jet coming from an inlet nozzle followed by an inlet channel attaches itself spontaneously to one of the side walls and flows along first and second main channels. A portion of the flow coming from the inlet channel is bled off by a reaction channel. This has the effect of detaching the jet from said wall and of causing it to attach to the opposite wall. The phenomenon repeats, thus giving rise to continuous oscillation in the incoming flow. The flow in the first and second main channels and in the reaction channel varies at a frequency that depends on the incoming flow rate. FIG. 1 shows an example of a fluidic oscillator as seen from above.
The oscillator 1 is symmetrical about a longitudinal plane of symmetry P and comprises an enclosure 3 defining an oscillation chamber 5 and an obstacle 7 received therein.
The enclosure 3 has an inlet opening 9 and an outlet opening 11 in alignment in the plane P with the fluid flowing through them in the direction indicated by arrows in the figure.
The inlet opening 9 is in the form of a slot of transverse size or xe2x80x9cwidthxe2x80x9d l that is small compared with a longitudinal dimension thereof referred to as its xe2x80x9cheightxe2x80x9d h and which lies in a plane perpendicular to the plane of FIG. 1 (see FIG. 2).
Conventionally, the width l is equal to about one-fifth of the height h.
This slot serves to transform a fluid flow into a jet of fluid that oscillates transversely in a plane perpendicular to the plane P, i.e. in a plane parallel to that of FIG. 1.
To obtain good metrological performance from an oscillator, it is necessary for the oscillation of the fluid jet to be under control, and in particular for the dimensions of the slot 9 to be accurately determined during manufacture of said fluidic oscillator.
The piece shown in FIG. 1 is made of aluminum, for example, and it is manufactured by operations of molding and of unmolding.
Nevertheless, it is not possible to make the piece directly with the desired dimensions merely by the operations of molding and unmolding.
Thus, a piece which has just been unmolded is subsequently machined in order to obtain the desired precision for its dimensions, and in particular for the dimensions of the slot 9.
The machining performed in particular on the slot 9 of the piece as unmolded is as shown in front view in FIG. 3.
In this figure, side portions 13 and 15 of the slot 9 as shown in dashed lines flowing through them in the direction indicated by arrows in the figure.
The inlet opening 9 is in the form of a slot of transverse size or xe2x80x9cwidthxe2x80x9d l that is small compared with a longitudinal dimension thereof referred to as its xe2x80x9cheightxe2x80x9d h and which lies in a plane perpendicular to the plane of FIG. 1 (see FIG. 2).
Conventionally, the width l is equal to about one-fifth of the height h.
This slot serves to transform a fluid flow into a jet of fluid that oscillates transversely in a plane perpendicular to the plane P, i.e. in a plane parallel to that of FIG. 1.
To obtain good metrological performance from an oscillator, it is necessary for the oscillation of the fluid jet to be under control, and in particular for the dimensions of the slot 9 to be accurately determined during manufacture of said fluidic oscillator.
The piece shown in FIG. 1 is made of aluminum, for example, and it is manufactured by operations of molding and of unmolding.
Nevertheless, it is not possible to make the piece directly with the desired dimensions merely by the operations of molding and unmolding.
Thus, a piece which has just been unmolded is subsequently machined in order to obtain the desired precision for its dimensions, and in particular for the dimensions of the slot 9.
The machining performed in particular on the slot 9 of the piece as unmolded is as shown in front view in FIG. 3.
In this figure, side portions 13 and 15 of the slot 9 as shown in dashed lines define the traditional tapering profile obtained after unmolding.
The machining operation then consists in eliminating the dashed-line portions 13 and 15 by means of a tool 17 such as a cutter which is inserted in the slot from above (as shown in FIG. 3) or through the opening that opens out into the oscillation chamber 5.
Nevertheless, since the slot is elongate in its height direction h and of narrow width l, the cutter 17 must be fine (e.g. having a diameter of 16 mm so as to give a width l equal to 19 mm), and as a result it is not strong enough mechanically.
Because of the fineness of the cutter, it can be subjected to mechanical vibration while it is being used, and as a result the surface state of the inside portion of the slot is not fully under control over its entire height, and in particular at the bottom thereof, i.e. close to the portion referenced 19 in FIG. 3.
In addition, because of its fineness, the cutter runs the risk of being damaged while it is in use. To avoid such damage, it is recommended to slow down the rate of machining, but that increases the duration of the machining operation and thus increases the economic cost thereof.
Such measures are difficult to accept in an industrial environment.
Furthermore, while machining, when the cutter leaves the slot via the upstream portion thereof (represented by reference 21 in FIG. 1) traveling in the direction opposite to the arrows in said figure, the tolerances on this portion coming directly from unmolding are poorly controlled.
This can be harmful since the conditioning of the fluid flow in this region must be fully controlled.
The present invention seeks to remedy at least one of the above-mentioned problems.
The present invention thus provides a fluidic oscillator that is symmetrical about a longitudinal plane of symmetry P, comprising an enclosure defining an oscillation chamber and having an inlet opening and an outlet opening through which the fluid flows and which are in alignment in said plane P in a xe2x80x9clongitudinalxe2x80x9d first direction A, said inlet opening being made in the form of a slot that is narrow in a second direction B extending transversely to said plane P and elongate in a third direction C parallel to said plane P and perpendicular to said longitudinal first direction A, wherein said slot is provided in an insert which is removable from said enclosure.
Thus, the removable insert and the enclosure of the fluidic oscillator can be manufactured separately: the removable insert and most particularly the slot are manufactured with precision while the enclosure can be manufactured more approximately.
It suffices during the molding and unmolding operations to provide a cavity of large dimensions inside the enclosure at the site where the slot is to be placed and then to machine in approximate manner the walls of the enclosure defining said cavity with a tool of larger dimensions than the tool used in the prior art.
The time required for machining the enclosure is thus reduced and the risk of damaging the tool is avoided.
More precisely, the removable insert has two side walls elongate in the third direction C and spaced apart in the second direction B so as to define between them the dimension of said slot in said second direction, and also referred to as its width l.
The removable insert may have two endpieces perpendicular to the third direction C and located at the two opposite ends of said side walls so as to define between said endpieces the size of the slot in the third direction, also referred to as its height h.
According to a characteristic of the invention, the removable insert is inserted in a cavity provided in the enclosure and of a transverse size d slightly greater than that of said insert.
Advantageously, the removable insert has a groove formed in a peripheral zone of said insert and contained in a transverse plane defined by the second and third directions, said peripheral groove being designed to receive a sealing member co-operating in particular with the walls of the enclosure which define the cavity.
In another embodiment of the invention, the side walls of the removable insert run into respective walls of the enclosure via at least one of their portions and they also extend beyond said portions in the xe2x80x9clongitudinalxe2x80x9d first direction so as to project into the oscillation chamber.
Thus, the walls projecting into the oscillation chamber serve to protect the fluid jet formed in the slot from external influences that could disturb the oscillation of said jet.
Advantageously, two corresponding sites are formed respectively on each of the endpieces upstream from the slot for the purpose of receiving an element which is suitable for modifying the speed profile of the fluid flow upstream from said slot.
The invention also provides an insert for incorporation in a fluidic oscillator as described above, said part comprising two side walls that are elongate in a direction C and that are spaced apart in a direction B perpendicular to the direction C in such a manner as to define a slot between them in said direction B.
The insert may have two endpieces perpendicular to the direction C and disposed at the two opposite ends of the side walls in such a manner as to define between said endpieces the size of the slot in said direction C.
Advantageously, a groove is formed in a peripheral zone of said insert and is contained in a plane defined by the first and second directions and, said groove being designed to receive a sealing member.
The side walls extend in a direction A perpendicular to a plane defined by the directions B and C in such a manner as to project into the oscillation chamber of the fluidic oscillator when said insert is incorporated therein.
The invention also provides a method of manufacturing a fluidic oscillator that is symmetrical about a longitudinal plane of symmetry P, the oscillator comprising an enclosure defining an oscillation chamber and having an inlet opening and an outlet opening through which the fluid flows and which are in alignment in said plane P in a xe2x80x9clongitudinalxe2x80x9d first direction, said inlet opening being made in the form of a slot which is narrow in a second direction extending transversely to said plane P and elongate in a third direction parallel to said plane P and perpendicular to said longitudinal first direction, wherein the method consists in making said enclosure by forming therein a cavity of transverse size greater than the transverse size of said slot, in manufacturing separately an insert and forming therein said slot, and in inserting said insert in said cavity.
More precisely, the method of the invention consists in making the enclosure of the fluidic oscillator by operations of molding and unmolding and then machining the unmolded enclosure.
The method of the invention also consists in making the insert by operations of molding and of unmolding.